Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation, or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been redesigned is the bicycle chain. Most bicycles have a drive train that uses a chain to transmit the pedaling action from the rider to the rear wheel. Bicycle chains have a plurality of inner links and a plurality of outer links that are interconnected in an alternating manner by a plurality of pins. Typically, each of the inner links includes a pair of parallel inner plates connected by a pair of parallel hollow cylinders or pins surrounded by cylindrical rollers. Each of the outer links includes a pair of parallel outer plates connected by the pins of the adjacent inner links.
Some bicycles are designed to be mountain bicycles (MTBs) which are suitable for traveling off-road. Some of MTBs only have a single front sprocket, and its gear ratio is only adjustable by the rear derailleur configured to move the chain between sprockets in the rear sprocket assembly. MTBs are frequently used in various terrains and often receive large impacts and vibrations which may cause the chain to fall off the front sprocket. Thus, MTBs experience higher stresses than other types of bicycles, such as road bicycles.
FIG. 1A schematically shows a plan view of a drive train 140 of a bicycle. A rear sprocket assembly 180 of the drive train 140 is arranged so that its intermediate-size sprocket substantially aligns with a front sprocket 160 in the longitudinal direction of the bicycle. A driving direction of a chain 120 is illustrated by an arrow DD. Thus, for example, when the chain 120 is engaged with the largest rear sprocket, a rear part of the chain 120 is largely pulled toward a frame of the bicycle, indicated via arrow F.
In such a case, as shown in an enlarged view of a part Q of FIG. 1, considering that the chain 120 is disengaged from one of the teeth 162 of a front sprocket 160 at one of inner link plate pairs, at a location DE, adjacent outer link plate pair to the inner link plate pair in the driving direction DD is axially inclined toward a frame of the bicycle, at a location LE. Thus, the sprocket tooth located within the outer link plate pair tends to contact an interior surface of the outer link plate. Since gaps between the outer link plates are wider in the axial direction compared to gaps between the inner link plate pairs, the sprocket teeth 162 have a wider range of relative movement within the gaps between the outer link plate pairs. This axial movement is the largest at the location LE, which may result in chain 120 undesirably falling off of the front sprocket 160, resulting in inconvenience to the rider.